Department of Chemistry, KAIST, Daejeon, Korea.
RNA Biol. 2020 Feb;17(2):176-187. doi: 10.1080/15476286.2019.1672514. Epub 2019 Sep 29.
RpoS is a key regulator of general stress responses in . Its expression is post-transcriptionally up-regulated by the small RNAs (sRNAs), ArcZ, DsrA and RprA, through sRNA- mRNA interactions. Although overexpression of the sRNA, CyaR, was reported to down-regulate expression, how CyaR regulates has not been determined. Here, we report that CyaR represses expression by base-pairing with a region next to the ArcZ binding site in the 5' UTR of mRNA and that CyaR expression itself is down-regulated by ArcZ through sRNA-sRNA interaction. The short form of ArcZ, but not the full-length form, can base-pair with CyaR. This ArcZ-CyaR interaction triggers degradation of CyaR by RNase E, alleviating the CyaR-mediated repression. These results suggest that ArcZ not only participates in translation as an activator, but also acts as a regulator of the reciprocally acting CyaR, maximizing its activating effect.
RpoS 是大肠杆菌中普遍应激反应的关键调节剂。其表达通过 sRNA（ArcZ、DsrA 和 RprA）与 mRNA 之间的 sRNA-mRNA 相互作用，在后转录水平上被上调。尽管据报道，sRNA CyaR 的过表达会下调 rpoS 的表达，但 CyaR 如何调节 rpoS 尚未确定。在这里，我们报告说 CyaR 通过与 rpoS mRNA 5'UTR 中靠近 ArcZ 结合位点的区域碱基配对来抑制 rpoS 的表达，并且 CyaR 的表达本身通过 sRNA-sRNA 相互作用被 ArcZ 下调。短形式的 ArcZ，但不是全长形式，可以与 CyaR 碱基配对。这种 ArcZ-CyaR 相互作用触发了 CyaR 被 RNase E 降解，从而减轻了 CyaR 介导的 rpoS 抑制。这些结果表明，ArcZ 不仅作为激活剂参与 rpoS 翻译，还作为相互作用的 CyaR 的调节剂，最大程度地发挥其激活作用。
